U.S. patent application number 14/776938 was filed with the patent office on 2016-02-25 for ion modification.
The applicant listed for this patent is Jonathan ATKINSON, David SHARP. Invention is credited to Jonathan Atkinson, David Sharp.
Application Number | 20160054263 14/776938 |
Document ID | / |
Family ID | 48226473 |
Filed Date | 2016-02-25 |
United States Patent
Application |
20160054263 |
Kind Code |
A1 |
Sharp; David ; et
al. |
February 25, 2016 |
ION MODIFICATION
Abstract
An ion mobility spectrometry method comprising determining
whether a sample comprises ions having a first characteristic, and
in the event that it is determined that the sample comprises ions
having the first characteristic, applying thermal energy together
with a radio frequency, RF, electric field to parent ions so as to
obtain daughter ions having a second characteristic for inferring
at least one identity for the parent ions based on the first
characteristic and the second characteristic.
Inventors: |
Sharp; David;
(Hertfordshire, GB) ; Atkinson; Jonathan;
(Hertfordshire, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHARP; David
ATKINSON; Jonathan |
Bushey, Watford, Hertfordshire
Bushey, Watford, Hertfordshire |
|
GB
GB |
|
|
Family ID: |
48226473 |
Appl. No.: |
14/776938 |
Filed: |
March 12, 2014 |
PCT Filed: |
March 12, 2014 |
PCT NO: |
PCT/GB2014/050744 |
371 Date: |
September 15, 2015 |
Current U.S.
Class: |
250/282 ;
250/287 |
Current CPC
Class: |
H01J 49/40 20130101;
H01J 49/0027 20130101; G01N 27/622 20130101 |
International
Class: |
G01N 27/62 20060101
G01N027/62; H01J 49/00 20060101 H01J049/00; H01J 49/40 20060101
H01J049/40 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2013 |
GB |
1304776.6 |
Claims
1. An ion mobility spectrometry method comprising: determining
whether a sample comprises ions having a first characteristic; in
the event that it is determined that the sample comprises ions
having the first characteristic, applying thermal energy together
with a radio frequency, RF, electric field to parent ions so as to
obtain daughter ions having a second characteristic for inferring
at least one identity for the parent ions based on the first
characteristic and the second characteristic.
2. The method of claim 1 in which determining whether the sample
comprises the ions having the first characteristic comprises
applying one of an RF electric field and thermal energy, to modify
a first plurality of ions derived from the sample.
3. The method of claim 1 in which applying the thermal energy
comprises applying thermal energy to a region of a spectrometer
drift chamber for a selected period.
4. The method of claim 3 in which the spectrometer drift chamber
comprises an electrode for applying the RF electric field, and the
thermal energy is localised within a selected distance of the
electrode.
5. The method of claim 1 in which applying thermal energy together
with the RF electric field comprises applying the thermal energy
prior to applying the RF electric field.
6. The method of claim 1 further comprising determining a
temperature of a region of a spectrometer drift chamber, and only
applying the thermal energy in the event that the temperature is
less than a selected threshold temperature.
7. The method of claim 1 in which applying thermal energy comprises
heating a region of a spectrometer drift chamber to a temperature
that is not sufficient to modify ions without the application of an
RF electric field.
8. The method of claim 1 in which applying thermal energy comprises
heating a region of a spectrometer drift chamber to a temperature
selected to promote ion modification by the RF electric field.
9. An ion mobility spectrometer comprising: a characteristic
determiner for determining a characteristic of ions of a sample; an
electrode adapted to subject the ions to an RF electric field in a
region of the spectrometer; a heater adapted to heat the region; a
controller configured to selectively control at least one of: the
application of an RF voltage to the electrode; and the heater; to
apply at least one of thermal energy and an RF electric field,
based on the determined characteristic.
10. The ion mobility spectrometer of claim 9 in which the
controller is configured to operate the electrode to apply one of:
an RF electric field and thermal energy; to a first plurality of
ions in the event that the characteristic determiner determines
that ions of the sample have a first characteristic, and then to
apply the RF electric field and thermal energy to a second
plurality of ions in the event that the characteristic determiner
determines that the first plurality of ions have a second
characteristic.
11. The ion mobility spectrometer of claim 9 in which the
characteristic determiner comprises a spectrometer drift chamber,
and a gate for controlling the passage of ions into the drift
chamber, wherein the controller is configured to operate the heater
to apply thermal energy for a selected period.
12. The ion mobility spectrometer of claim 9 in which the
controller is configured to operate the heater to apply thermal
energy in the event that the temperature is less than a selected
threshold temperature.
13. An ion mobility spectrometer comprising: an ion modifier
configured to apply an RF electric field to ions in a region of the
spectrometer; a heater configured to heat the region; and a
controller configured to operate the heater to heat the region
prior to operating the ion modifier to apply the RF electric
field.
14. The ion mobility spectrometer of claim 13 in which the heater
and the ion modifier are arranged such that the heater does not
prevent the RF electric field from modifying ions.
15. The ion mobility spectrometer of claim 13 comprising a drift
chamber, and a detector configured to detect the passage of ions
along the drift chamber, and a gate configured to control the
passage of ions into the drift chamber, in which the heater is
disposed in a position selected from the list consisting of: at a
drift gas inlet of the drift chamber; in the drift chamber between
the ion modifier and the gate; in the drift chamber between a
detector and the ion modifier; and carried by a wall of the drift
chamber about the ion modifier.
16. The ion mobility spectrometer of claim 13 in which the heater
is arranged to heat the region of the drift chamber more than other
regions of the drift chamber.
17. The ion mobility spectrometer of claim 13 comprising a drift
chamber, wherein the ion modifier is disposed in the drift chamber
and the spectrometer comprises a source of infrared radiation
arranged to apply infrared radiation to the localised region in the
drift chamber.
18. The ion mobility spectrometer of claim 13 in which the ion
modifier comprises the heater.
19. The ion mobility spectrometer of claim 13 comprising a
characteristic determiner for determining a characteristic of the
ions, wherein the controller is configured not to operate the
heater unless the characteristic determiner indicates the presence
of ions having one of a selected set of characteristics.
20. The ion mobility spectrometer of claim 13 comprising a
temperature sensor, wherein the controller is configured not to
operate the heater unless the temperature is less than a selected
threshold temperature.
Description
[0001] The present disclosure relates to apparatus and methods, and
more particularly to spectrometers, and to spectrometry
methods.
[0002] Ion mobility spectrometers (IMS) can identify material from
a sample of interest by ionizing the material (e.g., molecules,
atoms, and so forth) and measuring the time it takes the resulting
ions to travel a known distance under a known electric field. An
ion's time of flight can be measured by a detector, and the time of
flight is associated with the ion's mobility. An ion's mobility
relates to its mass and geometry. Therefore, by measuring the time
of flight of an ion in the detector it is possible to infer an
identity for the ion. These times of flight may be displayed
graphically or numerically as a plasmagram.
[0003] In some instances, modifying some of the ions using a radio
frequency, RF, electric field (e.g. by fragmenting them) to provide
additional information can be used to infer an identity for the
ions. This provides additional degrees of freedom in the
measurement of the ions, and therefore may improve the ability to
resolve differences between ions that may be difficult to
differentiate. Where measurements are performed in the presence of
contaminants, or in difficult operating conditions, or where a
sample comprises ions with similar geometries and masses etc. the
IMS's ability to detect and identify ions, and ion modification is
one way to address these issues.
[0004] Embodiments of the disclosure will now be described, by way
of example only, with reference to the accompanying drawings, in
which:
[0005] FIG. 1 is an illustration of a spectrometer;
[0006] FIGS. 2A to 2E are schematic diagrams of examples of
spectrometers to illustrate variations of the spectrometer
illustrated in FIG. 1; and
[0007] FIG. 3 is a flow diagram illustrating a method of operating
a spectrometer.
[0008] Embodiments of the disclosure relate to the selective
application of thermal energy in combination with an alternating,
e.g. RF, electric field to modify ions from a sample of interest.
This may enable less energy to be used to modify ions than may be
needed when an electric field or thermal energy are used alone.
This may enable portable spectrometry apparatus, such as hand held
and/or battery powered apparatus, to be operated with improved
efficiency.
[0009] An ion mobility spectrometer can determine whether a sample
comprises ions having a first characteristic, for example a time of
flight associated with one or more substances of interest. The ion
mobility spectrometer can then be operated to apply thermal energy
together with a radio frequency, RF, electric field to parent ions
so as to obtain daughter ions. The daughter ions may then have a
second characteristic (for example, a second time of flight), and
this may enable an identity, or a selection of candidate
identities, to be determined for the parent ions based on the first
characteristic and the second characteristic.
[0010] As another example of the disclosure, an ion mobility
spectrometer can comprise an ion modifier configured to apply an RF
electric field to ions in a region of the spectrometer, e.g. a
predefined region adjacent the ion modifier; a heater configured to
heat the region; and a controller configured to operate the heater
to heat the region prior to operating the ion modifier to apply the
RF electric field. This heating may be localised so that the region
is heated more than other regions of the spectrometer. For example,
the ion modifier may be arranged to apply an RF electric field to
ions in a region of a drift chamber of the spectrometer, and the
heater may be configured to heat that region more than other
regions of the drift chamber.
[0011] FIG. 1 is an illustration of an ion mobility spectrometer
(IMS) 100 which includes an ionisation chamber 102 that is
separated from a drift chamber 104 by a gate 106. The gate 106 can
control passage of ions from the ionisation chamber 102 into the
drift chamber 104. In FIG. 1, an ionisation source 110 is arranged
for ionising material in the ionisation chamber 102. As
illustrated, the IMS 100 includes an inlet 108 for enabling
material to be introduced from a sample of interest to the
ionisation chamber 102.
[0012] In the example illustrated in FIG. 1, the drift chamber 104
lies between the ionisation chamber 102 and a detector 118, so that
ions can reach the detector 118 by traversing the drift chamber.
The drift chamber 104 may comprise a series of electrodes 120a-d
for applying an electric field in the drift chamber to move ions
from the ionisation chamber along the drift chamber 104 toward the
detector 118.
[0013] The IMS 100 may be configured to provide a flow of drift gas
in a direction generally opposite an ion's path of travel to the
detector 118. For example, the drift gas can flow from adjacent the
detector 118 toward the gate 106. As illustrated, a drift gas inlet
122 and drift gas outlet 124 can be used to pass drift gas through
the drift chamber. Example drift gases include, but are not limited
to, nitrogen, helium, air, air that is re-circulated (e.g., air
that is cleaned and/or dried) and so forth.
[0014] The detector 118 may be coupled to provide a signal to a
characteristic determiner 200. Current flow from the detector 118
can be used by the characteristic determiner 200 to infer that ions
have reached the detector 118, and a characteristic of the ions can
be determined based on the time for ions to pass from the gate 106
along the drift chamber 104 to the detector 118. Examples of a
detector 118 are configured to provide a signal indicating that
ions have arrived at the detector 118. For example, the detector
may comprise a faraday plate, which may be charged to catch
ions.
[0015] Electrodes 120a-d may be arranged to guide ions toward the
detector 118, for example the electrodes 120a-d may comprise rings
which may be arranged around the drift chamber 104 to focus ions
onto the detector 118. Although the example of FIG. 1 includes a
plurality of electrodes 120a-d, in some examples only two
electrodes may be used, or a single electrode may be used in
combination with the detector 118 to apply an electric field to
guide ions toward the detector 118. Other electrode configurations
are also possible, examples include, but are not limited to
electrodes of other geometric shapes and electrically resistive
and/or conductive (e.g., a resistive electrical conductor)
coatings, such as a continuous coating.
[0016] A radio frequency, RF, electrode 126 can be arranged across
the drift chamber 104 such that ions passing from the ionisation
chamber to the detector pass the RF electrode. The RF electrode may
comprise a grid of conductors, which may comprise a metal such as
nickel. In one example, the conductors may be 20 microns in
diameter. In one example these conductors may be spaced 30 microns
apart. The RF electrode may comprise two electrodes, for example
two grids, which may be spaced apart. In one example the spacing
between the two grids may be 250 microns. The RF electrode may
subject ions in a region of the drift chamber 104 to an RF electric
field. Where the RF electrode 126 comprises two electrodes, the
region may be provided by the spacing between the electrodes.
[0017] In FIG. 1 the RF electrode 126 comprises a heater 127
arranged for providing thermal energy to the region of the drift
chamber in which the RF electrode 126 is arranged to subject ions
to an RF electric field. In the example of FIG. 1, the heater 127
comprises a resistive electrical conductor, which may be a part of
the RF electrode 126.
[0018] In the example illustrated in FIG. 1, the characteristic
determiner 200 is coupled to a controller 202, and the controller
can be configured to selectively control the application of an RF
voltage to the RF electrode 126; and heating by the heater 127.
Accordingly, the controller 202 can control the application of
thermal energy and/or an RF electric field, based on a
characteristic of ions determined by the characteristic determiner
200.
[0019] The spectrometer 100 may comprise a guard 123 which may
comprise a conductor arranged to provide an equipotential screen to
inhibit the electric field associated with an ion reaching the
detector before the ion actually arrives at the detector. This may
inhibit the detector from falsely detecting the arrival of an ion
before it reaches the detector 118. The guard 123 may be provided
by a conductive material, which may be arranged in a grid. The
guard 123 may be coupled to a selected voltage, for example by the
controller 202.
[0020] The spectrometer 100 may comprise a sensor 105 for sensing
the temperature in the drift chamber 104 and for providing a signal
based on the sensed temperature to the controller 202. The sensor
105 may be disposed in the drift chamber 104, for example the
sensor 105 may be carried by a wall of the drift chamber. The
temperature sensor 105 may comprise any sensor, such as an
electrical sensor (for example an electronic sensor) which may
comprise a thermistor or a thermocouple. The controller 202 may be
configured to obtain a signal from the temperature sensor 105, and
to enable operation of the heater 127 to apply thermal energy in
the event that the temperature is less than a selected threshold
temperature. For example the controller 202 may be configured so
that the heater 127 is not operated unless the temperature is less
than a selected threshold temperature.
[0021] In operation of the spectrometer 100, material from a sample
can be introduced into the ionisation chamber 104 via the inlet 108
where it can be ionised by the ionisation source 110. The
controller 202 can then operate the gate 106 to introduce ions into
the drift chamber 104 so the characteristic determiner 202 can
determine a characteristic of the ions (e.g. based on their time of
flight in the drift chamber 104).
[0022] The controller 202 may be configured so that, in the event
that the characteristic determiner 200 determines that ions from a
sample have a selected characteristic, such as a time of flight
associated with a substance of interest, a determination can be
performed to infer an identity for the ions. This may comprise
obtaining further ions from the sample, and operating the gate 106
to introduce these ions into the drift chamber 104. The controller
202 can then operate either the RF electrode 126 or the heater 127
to modify the ions, for example by fragmenting them and then
determining a first characteristic of those ions, e.g. a time of
flight of those ions.
[0023] The controller can also be configured so in the event that
the first characteristic of the modified ions comprises a selected
characteristic, such as a time of flight associated with a
substance of interest, the RF electric field and thermal energy can
be applied together to modify ions from the sample to determine a
second characteristic, which may be a subsequent measurement of the
same property of these modified ions, for example the time of
flight associated with the modified ions.
[0024] Applying thermal energy together with the RF electric field
may comprise the controller 202 being configured to operate the
heater 127 to apply thermal energy for a selected period prior to
operating the gate 106 to introduce ions into the drift chamber. In
embodiments the controller may be configured to apply thermal
energy together with the RF electric field by operating the gate
106 to introduce ions into the drift chamber 104, and then
operating the heater 127 to apply thermal energy to a region around
the RF electrode.
[0025] In FIG. 1 the RF electrode 126 comprises the heater 127. For
example, one or more conductors of the RF electrode 127 may be
coupled to receive an electric current for ohmic heating of the
electrode, this may comprise a current provided in addition to an
RF voltage used to apply the RF electric field, for example a DC
current may be passed through one or more conductors of the RF
electrode to provide heating.
[0026] The RF electrode 126 may not comprise the heater 127. In
addition, or as an alternative, the heater may comprise a grid of
conductors, which may be arranged across the drift chamber. In
embodiments where the RF electrode 126 comprises a grid, the pitch
of the heater grid (e.g. the spacing between adjacent conductors)
may be selected based on the pitch of the RF electrode 126. For
example the pitch of conductors in the heater 127 may be the same
as the pitch of conductors of the RF electrode 126, or the pitch of
the conductors of the RF electrode 126 may be an integer multiple
of the pitch of the conductors in the heater, or vice versa. In
these examples the arrangement of the conductors of the heater 127
and the RF electrode 126 may be arranged to correspond, for example
so a cross section of the drift chamber along which ions can pass
is not reduced by the presence of the heater. A grid of conductors
may include straight conductors arranged in parallel, for example
the conductors may be arranged in a lattice so that they cross one
another, or the conductors of a grid may be arranged so they do not
cross.
[0027] Where the RF electrode 126 does not comprise the heater 127,
the heater 127 may be arranged so that electrical interaction (e.g.
capacitive and/or inductive) coupling between the heater 127 and
the RF electrode 126 does not prevent the RF electrode 126 from
modifying ions.
[0028] The heater 127 may be spaced from the RF electrode 126 a
distance selected so the heater 127 does not prevent the RF
electrode 126 from modifying ions. Additionally, or as an
alternative, the geometry and/or orientation of the heater relative
to the RF electrode may be selected so it does not prevent the RF
electrode 126 from modifying ions. Additionally, or as an
alternative, the electric potential of the heater 127 may be
selected based on the electric potential of the RF electrode 126 so
that the presence of the heater 127 does not prevent the RF
electrode 126 from modifying ions. In some examples the heater 127
is arranged with respect to the RF electrode 126 so as to inhibit
capacitive and/or inductive coupling between the heater 127 and the
RF electrode 126. In some examples the voltage and/or impedance of
the heater 12 are selected to inhibit capacitive and/or inductive
coupling between the heater 127 and the RF electrode 126.
[0029] The heater 127 may be arranged between the drift gas inlet
122 and the RF electrode 126, for example the guard 123 may
comprise the heater 127. The heater may be arranged between the RF
electrode 126 and the drift gas outlet 124, for example the gate
106 may comprise the heater. In embodiments the electrodes 120a,
120b, 120c may comprise the heater. The heater may be arranged at
the drift gas inlet 122 to heat the drift gas on or prior to entry
into the drift chamber 104. The heater 127 may comprise a radiative
heat source, such as an source of infra-red radiation, for example
a laser which may be arranged to direct thermal energy to a region
of the drift chamber to which the RF electrode is adapted to apply
an RF electric field.
[0030] Applying thermal energy may comprise heating the region
around the RF electrode to a temperature that is insufficient to
modify ions without the application of an RF electric field. For
example, applying thermal energy may comprise heating the region to
a temperature of at least 30.degree. C., for example at least
35.degree. C., for example at least 40.degree. C. and/or to a
temperature of less than 120.degree. C., for example less than
100.degree. C. The controller 202 may be configured to control the
heater 127 based on a signal from the temperature sensor.
[0031] The characteristic determiner 200 may comprise a timer, and
the characteristic determiner may be coupled to determine the time
between the ions being introduced to the drift chamber, and one or
more ions being detected by the detector 118. The timing of the
ions being introduced to the drift chamber may be determined based
on operation of the gate 106.
[0032] The characteristic determiner may comprise a look up table
to enable characteristics of ions to be determined based on this
timing. The determined characteristic of the ions may comprise one
or more characteristics selected from the list comprising: the time
of flight of ions, the charge of the ions, the mass of the ions, a
mobility of the ions, and the mass/charge ratio of the ions. For
example the time of flight may be the time between the ions being
introduced to the drift chamber 104 and their arrival at the
detector, for example the time between operating the gate 106 to
allow ions into the drift chamber 104 and their arrival at the
detector 118.
[0033] The controller 202, and/or the characteristic determiner 200
may be provided by any appropriate controller, for example by
analogue and/or digital logic, field programmable gate arrays,
FPGA, application specific integrated circuits, ASIC, a digital
signal processor, DSP, or by software loaded into a programmable
general purpose processor.
[0034] FIGS. 2A to 2E are schematic diagrams of examples of
spectrometers to illustrate variations of the spectrometer
illustrated in FIG. 1.
[0035] In FIG. 1 and FIGS. 2A to 2E like reference numerals are
used to indicate like elements.
[0036] FIG. 2A illustrates a spectrometer 100-A which comprises a
heater 127 disposed in the drift chamber 104 between the detector
118 and the RF electrode 126. The heater 127 may comprise a
resistive heater, such as a grid of conductors arranged across the
drift chamber.
[0037] FIG. 2B illustrates a spectrometer 100-B which comprises a
heater 127 disposed in the drift chamber 104 between the ionisation
chamber 102 and the RF electrode 126. The heater 127 may comprise a
resistive heater, such as a grid of conductors arranged across the
drift chamber.
[0038] FIG. 2C illustrates a spectrometer 100-C which comprises a
heater 127-C disposed around the drift chamber 104 carried by a
wall of the drift chamber 104. The heater 127-C may comprise a film
heater for example comprising a resistive film or tape for heating
the region of the drift chamber 104 around the RF electrode
126.
[0039] FIG. 2D illustrates a spectrometer 100-D which comprises a
heater 127-D disposed at the drift gas inlet 122 for heating the
drift gas flowing into the drift chamber 104. The heater 127-E of
FIG. 2E may be disposed in and/or around the drift gas inlet, for
example it may comprise a resistive film, coating or tape carried
by a wall of the drift gas inlet 122. In addition, or as an
alternative, the heater 127-D of FIG. 2D may comprise a grid of
conductors arranged across the drift gas inlet.
[0040] FIG. 2E illustrates a spectrometer 100-E in which a
transmissive window 129 may be provided in a wall of the drift
chamber 104 to enable a radiative heat source 127-E to radiate
thermal energy into a region of the drift chamber comprising the RF
electrode 126.
[0041] FIG. 3 illustrates a method in which a spectrometry
measurement may be performed. In the event that the spectrometry
measurement provides an ambiguous result 298, the method may
comprise performing a further determination to resolve the
ambiguous result. In this case, the method comprises determining
300 whether a sample comprises ions having a first characteristic,
e.g. a selected time of flight. In the event that it is determined
that the sample does 302 comprise ions having the first
characteristic, the method may comprise obtaining 304 ions from the
sample and applying 306 energy to modify the ions so as to obtain
daughter ions. Applying 306 energy may comprise applying a radio
frequency, RF, electric field, or applying thermal energy, or
applying thermal energy together with a radio frequency, electric
field to those ions so as to obtain daughter ions.
[0042] A second characteristic of the daughter ions can then be
determined 308, e.g. the time of flight of the daughter ions. This
may enable an identity to be inferred 310 for the parent ions based
on the first characteristic and the second characteristic of the
daughter ions. The first characteristic and the second
characteristic may be subsequent measurements of the same parameter
e.g. the time of flight.
[0043] In some embodiments, in the event that a spectrometery
measurement performed without ion modification provides an
ambiguous result 298, the method may comprise obtaining 304 ions
from the sample and applying 306 a radio frequency, RF, electric
field, or applying thermal energy, to modify the ions to obtain
first daughter ions. A characteristic of the first daughter ions
can then be determined 308, e.g. the time of flight of the first
daughter ions.
[0044] To obtain further information, further ions can be obtained
from the sample and an RF electric field can then be applied to the
ions together with thermal energy, to modify the ions to obtain
second daughter ions. A characteristic of these second daughter
ions can then be determined 308, e.g. their time of flight. This
may enable an identity to be inferred 310 for the parent ions based
on the characteristic of the parent ions, and the characteristic of
the first and second daughter ions.
[0045] In a first method example, a method comprises determining
whether the sample comprises the ions having the first
characteristic comprises applying an RF electric field and/or
thermal energy, to modify a first plurality of ions derived from
the sample. In a second example applying the thermal energy
comprises applying thermal energy to a region of a spectrometer
drift chamber for a selected period prior or subsequent to
introducing ions into the region of the drift chamber. This second
example optionally includes the features of the first example. In a
third example the spectrometer drift chamber comprises an electrode
for applying the RF electric field, and the thermal energy is
localised within a selected distance of the electrode. This third
example optionally includes the features of either or both of the
first and second examples. In a fourth example applying thermal
energy together with the RF electric field comprises applying the
thermal energy prior to applying the RF electric field. This fourth
example optionally includes the features of any of one or more of
the first, second and third examples. In a fifth example the method
comprises determining a temperature of a region of a spectrometer
drift chamber, and only applying the thermal energy in the event
that the temperature is less than a selected threshold temperature.
This fifth example optionally includes the features of any of one
or more of the first to fourth examples.
[0046] In a first apparatus example an ion mobility spectrometer is
configured to apply one of: an RF electric field and thermal
energy; to a first plurality of ions in the event that a
characteristic determiner determines that ions of the sample have a
first characteristic, and then to apply the RF electric field and
thermal energy to a second plurality of ions in the event that the
characteristic determiner determines that the first plurality of
ions have a second characteristic.
[0047] In a second apparatus example, the characteristic determiner
comprises a spectrometer drift chamber, and a gate for controlling
the passage of ions into the drift chamber, wherein the controller
is configured to operate the heater to apply thermal energy for a
selected period. This second apparatus example optionally includes
the features of the first apparatus example.
[0048] In a third apparatus example, the controller is configured
to operate the heater to apply thermal energy in the event that the
temperature is less than a selected threshold temperature. This
third apparatus example optionally includes the features of the
first and/or second apparatus examples.
[0049] In a fourth apparatus example an ion mobility spectrometer
comprises an ion modifier configured to apply an RF electric field
to ions in a region of the spectrometer; a heater configured to
heat the region; and a controller configured to operate the heater
to heat the region prior to operating the ion modifier to apply the
RF electric field. This fourth apparatus example optionally
includes the features of the first and/or second and/or third
apparatus examples.
[0050] In a fifth apparatus example the heater and the ion modifier
are arranged so the heater does not prevent the RF electric field
from modifying ions. This fifth apparatus example optionally
includes the features of one or more of any of the first to fourth
apparatus examples.
[0051] It will be appreciated that in the context of the present
disclosure that RF electric fields comprise any alternating
electric field having frequency characteristics appropriate for
applying energy to modify ions (e.g. by imparting energy to them to
raise their effective temperature).
[0052] Other examples and variations will be apparent to the
skilled reader in the context of the present disclosure.
[0053] Aspects of the disclosure provide computer program products,
and computer readable media, such as tangible non-transitory media,
storing instructions to program a processor to perform any one or
more of the methods described herein. Other variations and
modifications of the apparatus will be apparent to persons of skill
in the art in the context of the present disclosure.
* * * * *